1. Field of the Invention
This invention relates to electrical contacts, and more particularly to electrical contacts of the type for receiving a component lead to establish electrical connection between the lead and a conductor of a printed circuit board. The invention also relates to improvements in insertion type contacts of the type fabricated from flat stock material by a stamping process, which have reliable insertion capabilities.
2. Description of the Prior Art
A type contact in wide use today with printed circuit boards is a contact having a pin at one end and a female receptacle at the other. This contact is inserted through a hole in a printed circuit board so that the female portion is engageably secured to the wall of the hole in the printed circuit board and the pin portion thereof extends through the printed circuit board and forms a terminal post for one or more wires. Such wires can be connected to the terminal post in the well known wrap-around means or any other suitable methods for securing a wire to a post. Components having male pin type terminals are then mounted on the circuit board by insertion of said male pins into the female portion of the inserted contacts.
In certain applications such as hand calculators, where space is at a premium, it is desired that the female portion of insertion type contacts have a low profile, i.e., the receiving opening of said female portion should be nearly flush with the surface of the printed circuit board. As a result of such low profile contacts components mounted therein will also be positioned close to the surface of the printed circuit board, thereby conserving space. Up to the present time such low profile insertion type contacts have been fabricated by screw machine techniques. Moreover, in most types of screw machine fabricated contacts it has been necessary to insert a spring in the female portion of the contact in order to make the structure capable of retaining a male pin subsequently inserted therein.
Furthermore, in contacts fabricated by a screw machine technique, the female portion consists of a closed cylindrical section having very little spring, or give. Thus, the tolerances of both the diameter of such female portions and also the diameter of the hole in the printed circuit board must be maintained within close limits. If the hole in the printed circuit board is too large compared to the diameter of the female portion of the contact, neither a good mechanical or a good electrical contact will be made when the contact is inserted therein. On the other hand if the aperture in the printed circuit board is too small, the plating on the walls of the printed circuit board hole is very apt to be scraped away when the contact is inserted therein, thus producing a poor electrical contact.
A further disadvantage of the screw machine type insertion contact lies in the fact that not one, but two, electrical contacts must be made. Firstly, the male pin inserted therein must make good contact with the female portion of the insertion contact, and secondly, the insertion contact must make good electrical contact with the wall of the printed circuit board hole since the male pin does not make direct physical contact with the wall of said hole.
Low profile contacts have been proposed in which the contact presents a single element stamped from a section of a continuously fed supply of flat stock material, and having a female receptacle portion thereof which engages the wall of a hole in a printed circuit board through which the contact is inserted. The female portion of the contact is generally cylindrical in configuration and includes a tang or finger which is stamp formed from a portion of the cylinder wall and extends inwardly from the cylinder wall into the center portion of the cylinder. When a male pin or contact lead is inserted into the cylinder, the pin is forced by the tang against the cylinder wall and the wall of the printed circuit board through an open portion presented in the cylinder. The top portion of the cylinder is ouwardly flared to assist in the subsequent insertion of a male pin or component lead. Because the cylindrical portion is not complete, that is, because it has a "C" shaped cross-section, a portion of the flared out top does not close completely, and it is possible that the male pin will miss the hole and get hung-up on the edge of the circuit board, especially in mass production or machine effected operations.